^^^ 

^ 


AUTHORS  EDITION.  COMPLIMENTS  OF  TilK  AUTHOR 


Alcatraz  Island, 

San  Francisco.  Cal, 


NOTES 


PAL/EOZOIC  CRUSTACE/E 


NO  2. 


UN  THE  NORTH  AMERICAN  SPECIES  OF  THE  GENUS  AGNOSTUS, 


(From  The  American  Gcoloijist,   Vol.  i  I' 1892) 


MINNEAPOLIS, 
JUNE,  1892. 


[Notes  on  Palaeozoic  Crustacew  No.  2.] 

ON  THE   NORTH  AMERICAN    SPECIES    OF  THE  GENUS 

AGNOSTUS. 

By  A.  W.  VoGDEs,  Fort  Canby,  Wash. 


{Fi'om  The  American  Geologist,  Vol.  IX,  June,  1892.'] 


[Notes  on  Pnhmzoic  CrustaceiV  No.  2.]  * 

ON     THE     NORTH    AMERICAN    SPECIES     OF     THE 

GENUS  AGNOSTUS. 

By  A.  W,  VoGDEs,  Fort  Canby,  Wash. 
HISTORICAL   SKETCH   OF   THE   GENUS   AGNOSTUS. 

The  earliest  known  species  of  this  genus  was  described  and  figured 
by  Bromell  in  1729,  Lithographia  Siiecana,  Actis  Liter.,  Suecia3,  Upsal, 
vol.  2,  p.  527,  under  the  name  of  Vermiculi  vagipenneg.  The  author  mis- 
takes the  fossil  for  an  insect  and  figures  Agnostvs  pisiformis  from  the 
Olenus  schist  of  Andrarum,  Sweden.  For  a  period  of  almost 
one  hundred  years  this  was  the  only  representative  of  a  genus,  to  which 
Brongniart  gave  the  name  of  Agnostus,  taking  for  its  type  Agnostvs  pisi- 
formis  from  Linn^'s  Entomolithus  pisiformis,  Syst.  Nat.  Ed.  xii,  p.  160. 

Dalman  uses  the  same  species  for  the  type  of  his  new  genus  Battus  in 
1826,  Paheaden  p.  257. 

In  the  5^ear  1828,  Dalman,  Vetensk,  Akad,  Arsber,  p.  136,  described  a 
new  species  from  Gothland  under  the  name  of  Battus  Imvigatus,  and  a 
new  variety  from  Andrarum,  as  Battus  pisiformis  var.  spiniger.  The 
next  contribution  to  our  knowledge  of  this  genus  was  made  by  Beyrich 
in  1845,  Ueber  Bohm  Trilobiten,  p.  44.  The  author  adds  two  new 
species  to  the  list  from  the  Paradoxides  zone  of  Bohemia,  under  the 

*No.  1  of  these  notes  is  published  in  Trans.  St.  Louis  Acad.  Sci.,  Vol, 
V,  1891. 


378  The  Araerican  Geologist. 


June,  1 


names  of  Battus  nudus  and  B.  integer.  The  discovery  of  an  entire  speci- 
men by  this  author  removed  the  doubts  regarding  the  affinities  of  these 
fossils  with  the  order  Trilobita. 

The  investigations  made  by  M'Coy  in  1846,  Syn.  Silurian  Fossils  of 
Ireland,  p.  56,  added  the  new  genus  TrinoduH  and  one  new  species,  T. 
agnostiformu.  The  non-adoption  by  palaeontologists  of  Tvinodus,  and 
the  imperfect  illustration  of  this  species  have  caused  several  identical 
forms  to  be  classed  under  new  names  such  as  Agnostus  convexus  Salt. 
A.  trinodus  Salt,  and  A.  tardus  Salt.,  Brit.  Pal.  Foss.  1851,  p.  141  (not  Bar- 
rande's  species).  The  species  ranges  high  up  in  the  geolog-c  column  as 
it  approaches  its  extinction,  in  the  zone  with  the  genus  Asaphus  and 
Trinucleus. 

Barrande  described  in  his  Preliminary  work  on  the  Silurian  System 
of  Bohemia,  1846,  pp.  14  and  35,  nine  new  species  under  this  genus; 
which  he  reduces  to  six  in  his  final  great  work  on  the  Bohemian  trilo- 
bites.  Etage  C  with  Parddoxides  hoheiidciu  contains — Agnostus  integer 
Beyr.,  A.  granulatusBa.TT.,  A.  nudus  Beyr.^  A.  hibuUutus  Barr.  and  A.  rex 
Barr.  Etage  D  with  Asiq^ltus  nob  ills  contains  Agnostus  tardus  Barr. 

Corda,  Prodrom  1847,  reclassifies  the  genus  into  seven  new  genera  and 
29  species.  All  the  genera  and  species  have  been  referred  to  well 
known  Bohemian  species  and  genera. 

In  the  Mem.  Geol.  survey,  vol.  2,  part  1,  p.  351,  pi.  8,  Salter  &  Phillips 
reproduce  under  the  name  of  Agnostus  trinodus  the  Irish  species  which 
M'Coy  described  as  Trinodus  agnostiforuiis.  The  authors  also  describe  a 
variety  of  this  species  as  connexus. 

1851 — Angelin  describes  and  figures  12  species  from  Sweden,  Pahieont. 
Scand.,  p.  5,  pi  6.  Regie  A  (Olenus  zone).  Agnostus  'jnsiforrnis  Linn^, 
A.  IcBvigatus  Dalm.,  A.  reticulatus  Aug.,  Regio  B  (Paradox ides  forchham- 
meri  zone),  Agnostus  planieauda  Aug.,  A.  exscu.lptus  Aug.,  A.  punctuosus 
Ang.,  A.  aculentus  Ang..  A.  hrenifrons  Ang.,  A.  glandiformis  Ang.,  A.  bituber- 
culatus  Aug.,  Regio  C  (Asaphus  zi  me),  Agnostus  lent  if orru  is  Aug.,  Regio 
D.,  Agnostus  glabratus  Ang. 

The  first  North  American  contribution  to  Agnostus  was  made  by  Bil- 
lings in  1860,  Canadian  Nat.,  vol.  5,  p.  302,  in  which  he  describes  from 
the  so-called  Quebec  group,  three  new  species,  Agnostus  americanus,  A.  ■ 
orion  and  A.  canadensis.  These  species  are  republished  in  Pa];i!Ozoic 
Fossils  of  Canada,  vol.  1,1865,  p.  395.  Agnostus  (imericunus  is  of  the  type 
Longifrontes,  congeneric  with  A.  trisectus  Salt,  which  occurs  at  An- 
drarum  with  Peltura  and  SpJucrophthalrnus.  A.  orion  differs  from  A.pisi- 
formis  by  having  the  glabella  proportionally  shorter.  Tlie  same  name 
was  used  by  Barrande  in  1846  for  a  species  of  the  genus. 

1860 — Eichwald,  Lethea  Rossica,  vol.  1,  p.  1351,  The  author  describes 
four  species,  two  of  which  are  for  the  first  time  illustrated — Agnostus  para- 
doxus Eichw.  and  .4.  nodiger,  n.  sp.  Eichwald  refers  A.  boeckii  to  A. 
exseulptus  Ang.     The  two  new  species  are  from  the  Asaphus  zone. 

1863 — An  important  contribution  to  American  paleontology  was  pub- 
lished during  this  year  by  James  Hall;  entitled  Preliminary  notice  of 
the  fauna  of  the  Potsdam  Sandstone,  16th  Report  N.  Y.  State  Cab.  Nat. 


The  American  Geologist. 


Vol.  IX,  Plate  IX. 


NORTH  AMERICAN   SPECIES  OF  AONOSTUS. 


Genus  Agnostics. —  Yogdes.  379 

Hist.  The  memoir  describes  the  fossils  of  the  Dikel»cephalus  zone  of 
Wisconsin.  In  this  work  we  have  illustrations  and  descriptions  of 
Agnostus  josepha,  A.  parilis  and  A.  disparilis.  The  first  species  ap- 
proaches A.  cyclopyge  Tull.  of  the  Olenus  zone  of  Sweden.  The  second 
is  of  the  type  Lsevigati  of  which  A.  Un-igatus  Dalm.  is  its  nearest  congen- 
eric form.  Dr.  Shumard  described  in  the  Am.  Jour.  Sci.,  vol.  32,  1861, 
p.  218,  Agnostus  coloradensis  from  Burnet  county,. Texas.  This  species  is 
of  the  type  A.  neron  H.  &  W. 

1864 — Salter  in  the  Mem.  Geol.  Survey,  Decade  XI,  describes  five  new 
species  of  the  genus  as  follows:  Agnostus  p>rinceps  alsovars.  ornatus  ard 
7'udis  (Olenus  zone).  (This  species  is  of  the  type  A.  atauus,  gihhus,  punc- 
tuosus,  ainericanus),  Agnostus  maccoyii.  Upper  Llandeilo  Flags,  Wales, 
A.  limbatus,  Caradoc,  A.  morea,  Lower  Llandeilo,  A.  tj-itiodus,  syn.  of  A. 
agnostiformis  M'Coy,  A.  trisectus,  Upper  Lingula.  (This  species  occurs 
at  Andrarum  with  PeUura2Jid.SpTnerophthalrnus). 

1865 — Billings  in  the  Palaeozoic  Fossils  of  Canada,  vol.  1,  redescribes 
A.  (onericanus,  A,  orion  and  A.  canadensis.  The  author  adds  two  new  spe- 
cies to  the  list  from  the  so-called  Quebec  group  of  Newfoundland, 
Agnostus  galha,  and  A.  fahicus.  The  former  species  differs  but  slightly 
from  A.  tardus  Barr.,  Etage  D,  in  Bohemia.  The  latter  approaches  A. 
lentiformis  Ang.,  Kegio  C,  of  Sweden. 

1866 — Schmidt  describes  a  new  species  in  the  Bull.  Acad.  Sci.,  St. 
Petersb ,  vol.  30,  1866,  p.  505,  fig.  45,  Agnostus  cyckanoicskii. 

1866— Linnarsson  describes  a  new  species  in  Om  de  Siluriska  bildnin- 
garne  i  Mellersta  ^Vestergotland;  Agnostus  affinis  from  the  zone  with 
Paradoxides   tessini. 

1867 — Belt  in  the  Geol.  Mag.,  vol.  4,  p.  294,  describes  Agnostus  nodosus 
and  .4.  pisiformis  var.  obesus,  from  the  "Upper  Cambrian"  of  Wales. 
Tullberg  remarks  that  A.  nodosus  Belt  is  probably  identical  with  A.  re- 
ticulatus  Ang.  The  author  illustrates  a  broad  and  narrow  form  of  A. 
pisiformis  var.  obesus.  In  vol.  5,  1868,  of  the  same  inagazine,  the  author 
describes  Agnostus  obtusus  from  the  Upper  Dolgelly  and  A.  harlowii  from 
the  Tremadoc. 

1868 — Barrande  describes  Agnostus  bavaricus,  in  Fauna  Silurienne  des 
environs  de  Hoff  en  Baviere,  p.  32,  figs.  46-47. 

1869 — Linnarsson,  Om  Vestergotland  Camb.  «&  Sil.  aflagringar.  The 
author  describes  8  species  of  Agnostus  including  the  following  new 
species,  A.  gibbus,  A.  2)arvifroas^  A.  sidenbladhi,  and  A.  fallax.  The  first 
two  species  occur  with  Paradoxides  tessini  at  Andrarum.  Agnostus 
sidenbladhi  ranges  higher  up  in  ihe  Ceratopyge  chalk. 

Sjogren  in  Om  nagra  forsteningar  i  Oland  Kambriska  lager  1871,  de- 
scribes Agnostus  regius  from  the  zone  with  Paradoxides  olandicus. 

1871— Hicks  in  the  Quart. Jour.  Geol.  Soc,  vol.27,  1^1,  p.  400,  de- 
scribes a  new  species,  Agnostus  cambriensis. 

1872— Meek  in  the  sixth  Report  U.  S.  Geol.  Sur.  Territories,  p.  664, 
gives  the  name  of  Agnostus  maladensis  to  a  species  from  Malade  City,. 
Utah;  and  that  of  Agnostus  bidens  to  one  from  Gallatin  City,  Montana. 

1872— Hicks  in  the  Quart.  Jour.  Geol.  Soc,  vol.  28,  1872,  p.  174,  de- 


380  The  American  Geologist.  june,i8j« 

scribes  five  species,  illustrating  a  new  one  under  the  name  of  Agnos- 
tus  eskriggei  from  near  Dolgelly,  Wales.  This  article  also  contains  de- 
scriptions of  Agnostus  davicUs  Salt.,  A  scutaUs  Salt.,  A.  scarceoides  Salt,  and 
A.  harrandei  Salt. 

1872 — Ford  illustrates  an  imperfect  trilobite  under  the  name  of  Ag- 
nostus nohilis  in  the  Amer.  Jour.  Sci.,  vol.  3,  1872,  p.  421.  This  species 
is  from  the  Olenellus  zone  near  Troy,  New  York,  and  may  prove  to  be  a 
species  of  the  genus  Microdiscus^  which  occurs  in  the  same  locality. 

1872 — Barrande  describes  three  new  species  from  Etage  D,  in  the 
Supplement  Syst.  Sil.  Bohm.,  vol.  1,  18T2:  Agnostus  caducus,  A.  perruga- 
tus  and  A.  similaris. 

1876— Kayser,  Beitnige  zur.  Geol.  «fe  Paheont.  der  Argentinischen  Re- 
publik,  p.  5.  The  author  describes  Agnostus  tilcuryensis  from  the 
Olenus  zone. 

1877 — White  in  his  Preliminary  Report  for  1874,  also  in  the  final  Re- 
port U.  S.  Geol.  Sur.,  west  100th  Mer.,  vol.  4,  1877,  describes  Agnostus  in- 
terstridus  from  Antelope  Springs,  Utah.  This  species  is  related  to  A. 
integer  Beyr. 

Hall  &  Whitfield  in  U.  S.  Geol.  Sur.  40th  Par.,  vol.  4,  1877,  describe 
four  new  species  from  the  Dikelocephalus  zone  of  Nevada:  Agnostus 
communis^  A.  neon,  A.  prolongus,  A.  tmiddosus. 

1878 — Hartt,  in  Dawson's  Acadian  Geology,  2d  Edition,  describes  A. 
acadicus  and  A.  similis ;  the  latter  species  is  now  included  as  a  synonym 
of  A.  acadicus. 

1878— Brogger,  Om  Paradoxide^skifrene  ved  Krekling,  describes  14 
species  including  the  following  new  forms,  Agnostus  gihhus  var.  hyhrida 
A.  JijenUJi,  A.  natliorsti,  A.  incertus,  A.  pavifrons  var.  mammilata,  also  var. 
nepos,  A.  nudus  var.  marginntas,  A.  p^unctuosus  var.  ajfinis  and  A.  trunca- 
tes.   All  these  species  occur  in  the  Paradoxides  zone. 

1880 — Tullberg,  in  his  excellent  monograph  on  the  Agnostus  species 
in  the  Cambrian  formation  at  Andrarum,  illustrates  and  describes  28 
species  of  this  genus  with  the  following  new  species:  Group  Longi- 
frons — Agnostus  fissus  Lund,MSS.,  A.  atavus,  A.  intermedius,  A.  elegans^ 
A.  lundgre?ii,  A.  cyclopyge,  A.  pusillus.  Group  Ltievigati — A.  cicer. 
Group  Limbati — A.  quadratus. 

Dames  in  Richthofin's  China,  vol.  4,  p.  27,  pi.  2,  describes  Agnostu» 
chinensis  from  the  Olenus  zone. 

1882— Holm,  in  Kongl.  Svenska  vet.  Akad.  Handl.,  vol.  6,  No.  9,  de- 
scribes A.  torquisti. 

1884— Walcott  in  Pahi?ont.  Eureka  Dist.  describes  six  species  includ- 
ing two  new  species:  Agnostus  seclusus  and  A.  richmondensis.  The  first 
species  is  of  the  type  A.  parvifrons  Linrs.  and  the  second  of  A.  natliorsti 
Brogger. 

1885— Matthew  in  the  Trans.  Roy.  J^oc.  Canada,  vol.  3,  describes  10 
species  from  the  Paradoxides  zone  of  St.  John:  Agnostus  regulus,  A. 
partihus,  A.  vir,  also  var  concinnus,  A.  acadicus  Hartt,  var.  decliris,  A.  tes- 
sella,  A.  umbo,  A.  ohtusilohus  and  A.  acutilohus. 


Genus  Agnostits. —  Vogdes.  381 

1889— Walcott  describes  in  the  Proc.  Natl.  Mus.  vol.  12,  1889,  the  only 
known  American  Olenellus  zone  Agnostus,  under  the  name  of  A.  desid- 
emtus,  from  Salem,  New  York.  This  species  is  illustrated  in  the  10th 
Report  U.  S.  Geol.  Survey,  p.  630,  pi.  80,  fig.  5. 

RECAPITULATION  * 

From  the  Olenellus  zone,  Agnostus  nobilis  Ford,  A.  desider- 

atus  Walcott,  A.  fallax  Liurs 3 

From  the  Paradoxides  zone 44 

From  the  Olenus  zone 6 

From  the  Dikelocephalus  zone 19 

From  the  Asaphus  zone 18 

~9U 
AGNOSTUS,  Brongniart,  1822. 
Diagnosis. — The  general  form  of  the  body  of  the  Agnosti  is 
elongated  elliptical,  the  surface  convex.  The  head  presents  the 
same  structure  as  that  part  in  other  trilobites,  with  the  exception 
of  eyes  and  facial  suture,  which  are  wanting  in  this  genus.  The 
glabella  determined  by  the  dorsal  grooves,  never  extends  to  the 
anterior  contour;  it  is  always  prominent  by  its  relief;  its  form 
varies  with  the  species.  The  typical  form  has  a  glabella  divided 
into  a  small  frontal  lobe,  and  a  larger  posterior  lobe;  the  basal 
lobes  forming  a  third  part.  The  frontal  lobe  is  usually  subtrian- 
gular  having  a  groove  in  front  {A.  pisiforniis,  plate  ix,  fig.  14), 
In  the  section  Limbati,  the  glabella  is  broadly  rounded  in  front, 
showing  a  great  development  as  in  ^4.  rex,  plate  x,  fig.  13.  In 
the  section  Parvifrontes,  the  glabella  has  only  a  single  lobe,  as  in 
A.  parvifrons,  plate  x,  fig.  12.  In  the  typical  glabella  the  pos- 
terior lobe  exhibits  an  inclination  to  divide  laterally,  or  in  front, 
being  marked  by  a  medium  ridge.  The  glabella  is  sometimes 
compressed  on  the  sides  by  the  basal  lobes,  but  expands  at  this 
point  again  in  its  posterior  projection,  as  in  A.  gihJnis.  The 
basal  lobes  are  very  short,  so  that  in  A.  gibbus,  they  appear  like 
a  narrow  band  widening  out  on  both  sides  of  the  head,  forming 
two  nodes,  which  are  sometimes  large  and  triangular,  as  in  the 
section  Fallaces.  The  basal  lobes  are  divided  in  some  species 
into  two  nodes  on  each  side,  as  in  A.  atavus,  but,  they  are  gener- 
ally very  minute.  The  occipital  groove  and  ring  are  more  or  less 
developed.  The  lateral  lobes  of  the  head  form  a  concentric  band 
with  the  contour;  this  is  called  by  Barrande  the  genal  zone.  In 
the  section  Longifrontes,  the  cheeks  in  front  of  the  glabella  are 
divided  by  a  furrow  extending  from  the  apex  of  the  glabella  to 

*The  varieties  are  omitted  in  this  enumeration. 


382  The  American  Geologist.  June,  1892 

the  limb.  The  surface  of  the  genal  zone  is  smooth  in  the  section 
Limbati,  but,  in  Longifrontes  they  show  a  tendency  to  striate  or 
punctate.  The  limb  around  the  head  is  always  wider  in  front  and 
narrowed  towards  the  thorax.  One  can  distinguish  upon  its  surface 
an  internal  groove,  and  an  external  ridge  forming  the  contour, 
sometimes  the  limb  is  extended  into  small  points  on  each  side,  as 
in  A.  josepha.  In  the  section  Lsevigati  the  limb  becomes  obso- 
lete; in  the  section  Limbati  it  is  broad.  The  thorax  has  two 
segments  in  all  the  know^n  species.  The  axis  is  usually  well  de- 
veloped in  width,  whereas  the  pleurae  are  often  reduced;  when 
the  trilobation  is  distinct,  as  in  A.  rex,  the  thorax  shows  the 
same  characteristic;  when  it  is  faint,  as  in  A.  muUs,  the  triloba- 
tion is  also  indistinct.  The  first  segment  is  subdivided  b}'  a  groove 
w^hich  gives  to  the  pleurae  two  bands  more  or  less  elevated,  the 
anterior  band  being  the  larger;  the  second  segment  has  the 
pleurae  on  each  side  divided  into  bands  of  equal  width;  the 
points  of  each  pleura?  are  directed  forward.  The  pygidium  con- 
forms to  the  head.  In  certain  species,  for  example  A.  hilmUatus^ 
the  pygidium  is  marked  with  dorsal  grooves;  but  the  head  show& 
no  trace  of  these  grooves.  In  A.  rex  the  axis  of  the  p3'gidium 
reproduces  that  of  the  thorax.  The  lateral  lobes  form  a  concen- 
tric zone  to  the  contour  sometimes  united,  but  often  separated 
behind  the  axis.  The  limb  surrounding  the  pygidium  is  some- 
times extended  into  points.  If  tlie  head  has  no  border,  that  of 
the  pygidium  is  augmented  as  in  A.  nudis.  The  t3'pical  axis 
occupies  generally  f  of  the  total  length.  In  front  of  the  axis  is 
located  a  small  triangular  border  (genou  articulaire).  The  axis 
has  three  joints;  the  center  lobe  is  usually  the  smallest,  but  at- 
tains the  greatest  hight ;  it  carries  typically  on  the  medium  line  a 
node,  which  sometimes  is  extended  backwards  over  the  third 
joint  (-1.  nathorsH  and  A.  acnJcafus),  also  extended  into  a  spine 
in  A.  gihhns.  In  A.  rex  the  middle  joint  on  the  axis  is  divided 
by  a  groove,  into  an  upper  and  lower  lobe.  The  anterior  joint 
of  the  axis  has  an  inclination  to  become  separated  into  three 
lobes;  the  two  side  lobes  are  common.  The  last  joint  is  heart- 
shaped.  '  In  ^4.  rex  the  last  joint  is  short  and  rounded;  in 
A.  cyclopyge  it  is  large  and  rounded.  Sometimes  the  axis  is 
long,  A.  fallax.  The  side  lobes  when  the  axis  is  short  unite  be- 
hind it.  In  the  typical  species  they  are  divided  by  a  furrow, 
which  often  becomes  obsolete.      In  A.  hjerulji  and  A  p)^i^nicauda 


Genus  Agn  ostics.  —  Vogdes.  383 

an  elevated  ridge  extends  from  the  spines  of  the  pygidiiim  to  the 
axis. 

In  the  section  Lcevigati^  the  dorsal  grooves  are  limited  on  the 
head,  only  partly  defining  the  glabella;  they  are  also  limited  on 
the  pygidium,  especially  in  rear,  as  in  A.  Icevigatus  Dalm. ,  plate 
X,  fig  3.  In  the  section  Arthrorhachis  the  glabella  is  prominent, 
long  and  marked  with  small  basal  lobes;  the  axis  of  the  pygidium 
is  short,  as  in  Agnostus  tardus  Barr. 

PART  3.  DESCRIPTION  OF  THE  NORTH  AMERICAN  SPECIES. 
The  insignificant  genus  Agnostus  surpasses  in  number  of  spe- 
cies all  the  other  genera  of  the  order  Trilobita;  in  the  primordial 
fauna  we  have  a  total  number  of  ninety  species,  excluding  the 
Varieties.  The  species  range  from  the  Olenellus  zone  to  the 
Lower  Silurian.  The  zone  with  Paradoxides  contains  44  species 
and  several  varieties;  the  Olenus  is  not  so  well  represented:  but, 
the  genus  outlived  both  these  genera  and  extends  into  the  Cera- 
topyge  chalk  (.4.  sideadladhi)  also  in  the  Orthoceras  zone 
{A.  lentiformis  &c).  The  genus  dies  out  in  the  zone  with 
Asaphus  and  Trinucleus  (^4.  trinodus  &c).  In  North  America 
the  genus  is  represented  by  twenty-eight  species  which  may  be 
arranged  into  the  following  zones  and  sections: 

OLENELLUS  ZONE. 

Agnostus  nobilis  Ford,  1872. 

This  is  a  doubtful  species  and  may  belong  to  the  genus  Micro- 
discus. 

Section  I,  PARVIFRONTES.— The  glabella  is  only  partly  de- 
veloped in  this  section  {Agnostus  hrevi/rons  Aug.,  plate  X,  fig.  12). 

Agnostus  desideratus  Walcott,  1890. 
Plate  X,  fig.  7.  Cf.  Agnostus  jn-olongus  Hall. 
Diagnosis.  Head  about  as  broad  as  long,  broadl}'  rounded  in 
front,  sides  curving  in  slightly  towards  the  posterior  margin, 
which  slopes  obliquely  inwards  from  the  posterolateral  angles  to 
the  glabella.  The  glabella  is  less  than  f  the  length  of  the 
head.  A  narrow  raised  rim  extends  all  around  the  margins,  ex- 
cept across  the  base  of  the  glabella,  which  is  subcylindrical,  nar- 
row, with  a  small  node  on  the  posterior  third  of  its  medium  line. 
Surface  smooth.      Locality,  Salem,  N.  Y.     This  species  is  of  the 


384  The  American  Geologist.  June,  i892 

type  A.  pan- if  mm  Linrs.  which  appears  with  the  genus  Fara- 
doxidea  in  Norway.  The  pygidium  of  A.  jrroJongus  Hall,  pi.  x, 
fig.  10,  has  a  similar  form  to  the  head  of  this  species.  The 
author  illustrates  only  the  head.  An  associated  pygidium  has  a 
prominent  axis  bordered  by  a  narrow  convex  space  between  it 
and  the  limb.  The  axis  does  not  exhibit  lateral,  or  transverse 
furrow.      An  elongated  median  tubercle  is  the  only  ornament. 

PARADOXIDES  ZONE. 
Section  II,  LONGIFRONTES-  This  section  is  distinguished  by 
its  strongly  projecting  glabella  and  axis,  which  latter  is  generally 
moderately  long.  Crust  smooth.  The  cheeks  grooved.  The  crust 
on  the  cheeks  and  pygidium  is  provided  with  raised  points. 
Limb  generally  narrow.  The  cheeks  in  front  of  the  glabella  and 
side  lobes  of  the  pygidium,  behind  the  axis,  divided  by  a  groove. 
{Agnostus  imnctnosuH  Kng.,  pi.  IX,  fig,  2,  also  yl.  pUiformis  pi. 
IX,  fig.  14). 

Agnostus  acutilobus  Matthew,  1885.      Plate  ix,  fig.  1. 

I)iag)iosis. — Body  elliptical,  elongated.  Head  semi-elliptical. 
Dorsal  furrow  faint,  marginal  furrow  and  fold  sharply  defined. 
Glabella  subconical,  length  f  of  that  of  the  head.  The  glabella 
is  divided  into  two  lobes ;  the  anterior  lobe  is  ^  of  the  length  and 
subtriangular,  posterior  lobe  extends  to  the  base  of  the  head.  It 
has  an  elongated  ridge  on  the  anterior  half,  with  two  faintly 
marked  lateral  furrows  on  the  lateral  edges  of  this  lobe.  The 
basal  lobes  are  divided  off  by  a  sigmoid  farrow  and  depressed 
below  the  level  of  the  glabella.  Occipital  ring  narrow.  The 
cheeks  are  somewhat  full  especially  in  front  and  divided  by  a 
furrow,  each  cheek  is  seamed  across  by  a  faint  furrow.  Thorax 
of  two  segments ;  the  first  has  five  lobes,  the  second  onl}^  three. 
Pygidium  subelliptical.  Axis  is  oblanceolate,  nearl}'  ^  as  wide 
as  the  pygidium  and  its  length  is  about  f  of  that  of  the  pygi- 
dium, narrowed  in  the  anterior  third,  and  crossed  in  that  part  by 
two  transverse  furrows;  the  included  lobe  bears  an  elongated 
tubercle ;  lateral  lobes  of  the  p3^gidium  moderately  elevated  and 
united  behind  the  axis.  Surface  smooth  externally,  but  it  is 
granulated  on  the  inner  surface  of  test. 

Locality.    St.  John  group,  Porter's  brook,  St.  Martin's. 


Genus  Agnostus. —  Yogdes.  385 

The  species  differs  in  minor  points  from  A.  gihhus  var.  hyhridus  Brog- 
ger,  especially  in  having  an  elongated  ridge  on  the  front  of  the  posterior 
lobe  of  the  glabella. 

Agnostus  obtusilobus  Matthew,  1885.      Plate  ix,  fig.  3. 

Cf.  A.  scarceoides  Salter,  1872,  from  which  it  differs  by  a  nar- 
rower glabella  with  a  more  obtuse  frout. 

Diagnosis. — The  head  of  this  species  is  like  that  of  A.  acuti- 
loha  Matthew.  The  pygidium  described  under  this  name  is  sub- 
quadrate  in  form,  wider  behind  than  before,  and  has  a  pair  of 
spines  at  the  outer  angles.  The  axis  is  nearly  one-half  as  wide 
as  the  pygidium,  about  four-fifths  of  its  length  and  projects  for- 
ward beyond  the  side  lobes ;  it  is  obtusely  lanceolate,  somewhat 
narrowed  in  the  middle,  and  divided  into  three  lobes,  of  which 
the  posterior  is  a  ^  longer  than  the  length  of  the  two  anterior. 
The  middle  lobe  is  elevated  in  the  middle,  and  bears  an  elongated 
tubercle  on  the  axial  line;  there  is  also  a  faint  tubercular  eleva- 
tion on  the  middle  of  the  anterior  lobe.  The  lateral  lobes  of  the 
pygidium  are  somewhat  narrowed  in  the  middle  of  their  length  by  - 
the  projecting  sides  of  the  axial  lobe,  and  rapidly  behind  the 
pygidium,  where  they  connect.  The  dorsal  furrow  is  deepl}"  im- 
pressed all  around,  and  at  the  posterior  angle  is  ver}'  close  to  the 
marginal  furrow;  this  furrow  is  angled  forward  to  the  axial  lobe 
and  quadrately  rounded  at  the  posterior  side  of  the  pygidium. 
Locality.     St.  John  group,   Porter's  and  Hanford  brooks,  St.  Martin's. 

Agnostus  tessella  Matthew,  1885.  Plate  ix,  fig.  4. 
Diagnosis. — Head  semi-elliptical,  higher  in  the  middle  and 
rear  part.  Dorsal  furrow  distinct  on  the  posterior  f  of  the  gla- 
bella, faint  on  the  other  ^.  Limb  strongly  elevated ;  the  interior 
groove  deep  and  strongly  impressed.  Griabella  cylindro-conical, 
rounded  in  front,  the  width  ^  of  that  of  the  head;  the  length  five- 
sevenths.  The  frontal  lobe  of  the  glabella  is  depressed  to  the 
level  of  the  cheeks,  and  almost  obsolete;  the  posterior  lobe  is 
cylindrical,  rounded  behind,  bounded  in  front  by  a  straight,  deep 
furrow,  and  bears  a  small  tubercle  ^  from  the  front.  Basal  lobes 
small.  '  Thorax  of  two  segments.  The  anterior  segment  bears 
five  lobes  of  which  the  two  lateral  pairs  are  globose;  the  axis  is 
transversely  elongated,  wider  behind  than  before,  and  bears  a 
minute  tubercle  at  the  axial  line.      The  posterior  segment  is  simi- 


386  The  American  Geologist.  .       June,  i892 

lar  except  the  tubercle.  The  pygidium  is  semi-elliptical,  some- 
what wider  than  long,  strongly  elevated  along  the  axis,  trun- 
cated in  front  at  the  lateral  thirds.  The  axis  is  cylindro-conical, 
width  ^  the  pygidium,  length  f;  it  bears  an  elongated  tubercle 
on  the  axial  line  at  the  anterior  \ ;  short  furrows  indent  the  sides 
of  the  axis,  opposite  the  ends  of  this  tubercle.  The  side  lobes 
are  narrow  and  divided  at  the  extremity  of  the  axis  by  a  furrow, 
connecting  the  dorsal  and  marginal  furrows. 
Lomlity.     St.  John  group,  at  Porter's  brook,  St.  Martin's. 

\gnostus  acadicus  Hartt,  1878.  Plate  ix,  fig.  7.  Syn.  Aguostus 
similis    Hartt. 

Diagnosis. — Head  convex,  depressed.  Limb  narrow,  slightly 
elevated.  Glabella  slightly  less  than  f  of  the  length  of  the  liead^ 
long,  elliptical,  depressed  convex,  but  more  elevated  than  the 
other  parts  of  the  head ;  frontal  lobe  of  the  glabella,  sub-circular 
and  occupying  about  ^  of  the  glabella;  basal  lobes  small,  but 
distinct.  Cheeks  of  the  same  width  throughout  and  united  in 
front  of  the  glabella;  they  are  convex,  more  elevated  along  their 
inner  margins,  but  sloping  outwards  roundly  and  evenly.  The 
genial  zone  has  a  narrow,  shallow,  flat  space  or  groove  which  fol- 
lows the  limb;  on  going  posteriorly  along  the  lateral  margins  it 
loses  gradually  its  width  towards  the  posterior  angles  of  the  head. 
Thorax  unknown. 

Pygidium  similar  to  the  head.  The  limb  slightly  raised,  separ- 
ated from  the  sides  by  a  shallow  but  well  marked  groove  running 
parallel  to  the  margin.  This  groove  widens  at  the  point  where  it 
bends  to  go  forward  along  the  sides,  in  such  a  way  as  to  en- 
croach on  the  thin  out  of  the  limb;  just  before  reaching  the  an- 
terior margin  it  narrows  itself  from  the  inner  side,  so  as  to  cause 
the  side  lobes  to  widen  somewhat  anteriorly.  These  are  narrow, 
flattened,  about  ^  as  wide  as  the  axis,  narrowing  to  a  point  just 
behind  the  axis  where  they  do  not  unite.  The  axis 
is  about  five-sixths  of  the  length  of  the  p3'gidium,  lan- 
ceolated,  flattened,  more  elevated  than  the  side  lobes  of  the  P3'gi- 
dium.  Dorsal  furrows  distinct.  The  axis  has  a  small  tubercle 
located  on  the  median  line  about  ^  its  length  from  the  front  mar- 
gin.     Surface  smooth. 

Locality.     St.  John  group,  Saiat  John,  N.  B. 

The  head  of  this  species  approaches  that  of  A.neon,  Hall  &  Whitfield. 


The  A31ERICAN  Geologist. 


Vol.  IX,  Plate  X. 


NORTH  AMERICAN  SPECIES  OF   AGNOSTUS. 


{•OlSlTttSllYl 
Z4l 


Genus  Agnostics. —  Vogdes.  387 

Agnostus  acadicus  var.  declivis  Matthew,  1885.   ,P1.  ix,  fig.  8. 
The  author  compares  this  species  with  A.  secretus  Walcott. 

Agnostus  regulus  Matthew,    1885.     Plate  x,  fig.  11. 

Diagnosis. — Head  elongate,  semi-elliptical,  with  straight  sides^ 
posterior  contour  .broken  by  the  projecting  glabella,  and  narrow 
occipital  ring.  Dorsal  furrow  distinct,  marginal  furrow  and 
limb  sharply  defined;  the  latter  diminishes  towards  the  posterior 
angles  of  the  head.  Glabella  large,  consisting  of  two  lobes;  the 
anterior  lobe  semi-circular,  wider  than  the  posterior  lobe,  elevated 
above  the  general  contour  of  the  surface  and  undulate  with 
broad  furrows,  radiating  from  the  back  of  the  lobe;  posterior 
lobe  flattened,  cylindrical,  with  a  faint  broad  median  transverse 
furrow  interrupted  at  the  summit  of  the  glabella  by  a  node, 
elongated  on  the  line  of  the  axis.  The  cheeks  are  narrowed  in 
the  middle,  there  being  a  crescent-shaped  limb  in  front  of  the 
anterior  lobe  of  the  glabella,  and  an  expanding  cheek  on  each 
side  of  the  posterior  lobe  of  the  glabella. 

The  pygidium  is  elliptical.  The  axial  lobe  large,  high,  obtusely 
Clavate,  constricted  in  the  centre  and  divided  into  three  lobes; 
the  middle  lobe  is  larger  than  the  combined  length  of  the  other 
lobes,  and  has  a  median  ridge-like  tubercle.  This  lobe  is  indented 
in  the  middle  of  its  length  on  each  side  by  a  short  furrow ;  the  an- 
terior lobe  is  narrow  and  ring-like;  the  posterior  lobe  is  sub- 
lunate.  Limb  distinct.  The  side  lobes  of  the  pygidium  narrow 
in  rear  to  conform  with  the  axis. 

Locality.  St.  John  group,  at  Portland,  Hanford  and  Porter's  brook, 
St.  Martin's. 

This  species  is  of  the  type  A.  rex  Barr. 

Section  PARVIFRONTES. 
Agnostus  umbo  Matthew,  1885.  Plate  x,  fig.  9. 
Diagno.ns. — Head  broadly  transversely  elliptical,  high  and 
contracted  behind,  sloping  from  the  glabella  in  all  directions. 
Marginal  fold  and  furrow  strongly  marked.  Dorsal  grooves  dis- 
tinct. Glabella  suborbicular,  rounded  in  front,  and  behind 
bearing  a  small  tubercle  on  the  axial  line,  ^  from  the  front. 
Length  of  the  glabella  ^  that  of  the  head.  Pygidium  semi-ellip- 
tical. Dorsal  and  marginal  furrows  deeply  impressed;  axis  coni- 
cal and  greatly  elevated  above  the  rest  of  the  pygidium;  it  bears 
a  small  tubercle  ^  from  the  front.      The  limb  is  rather  wide  at 


^P^  OP  thb'^C^ 


388  The  American  Geologist.  June,  i892 

the  extremity,  of  the  pygidium,  and  is  rounded  at  the  anterior 
corners. 

Locality.    St.  John  group,  at  Porter's  brook. 

This  species  is  of  the  type  A,  %)ctrvifrons  Linrs. 

Section  III,  LIMBATI.  (xeneral  form  subquadrate,  head 
has  a  broad  limb,  basal  lobes  large.  The  cheeks  in  front  of  the 
glabella  are  not  divided  by  a  central  groove  or  grooved  at  the 
sides.  The  p3'gidium  is  usually  produced  into  lateral  spines. 
{Agnostus  rex  Barr,  pi.  x  fig.  13). 

Series  A.  (REGII).  Distinguished  by  its  broad  limb,  dimin- 
ishing cheeks  and  side  lobes  of  the  pygidium.  Both  the  anterior 
lobe  of  the  glabella  and  the  posterior  lobe  of  the  pygidium  ex- 
pand.     (Type  Agnostus  rex  Barr). 

Series  B.  (FALLACES).  This  series  has  a  smaller  head,  and 
moderately  broad  limb.  Cheeks  large;  basal  lobes  rather  large 
with  a  broad  posterior  lobe  to  the  axis  of  the  pygidium.  (Type 
Agnostus  f alia X  Linrs,  pi.  x,  fig.  2). 

Agnostus  vir  Matthew,  1885.      Pi.  x,  flg.  14. 

Diagnosis. — Head  elongate,  semi-elliptical,  with  straight  sides 
and  angulated  behind.  Dorsal  furrow  distinct.  Marginal  fold 
and  groove  rather  flat  and  broad.  G-labella  subconical,  obtuse  in 
front,  expanded  ])ehind.  Length  about  five-sevenths  of  that  of 
the  head.  The  anterior  lobe  of  the  glabella  is  about  two-fifths 
of  its  length;  it  is  elliptically  rounded  in  front,  and  obtusely 
behind;  the  posterior  lobe  is  narrowed  behind,  and  in  that  part  is 
decidedly  elevated  above  the  rest  of  the  head;  a  sigmoid  furrow 
cuts  ofl['  a  depressed  basal  lobe  on  each  side.  The  cheeks  are 
moderateh'  elevated,   and  of  equal  width  all  around  the  glabella. 

The  thorax  consists  of  two  segments,  the  first  is  divided  into 
three  lobes  of  which  the  outer  pair  is  globose,  the  axis  is  elon- 
gated, transverse  and  indented  on  the  front  side  by  two  strong 
furrows  extending  ^  wa}^  across ;  the  second  segment  is  similar  to 
the  first,  except  that  there  are  no  grooves  on  the  axis. 

The  pygidium  is  subquadrate,  and  armed  with  two  lateral 
spines:  its  width  one-fifth  greater  than  its  length.  Axis  cylin- 
dro-conical,  obtusely  pointed  behind,  and  bears  an  elongated 
tu])ercle  pointed  backwards.  The  side  lobes  of  the  pygidium  are 
about  ^  the  width  of  the  axis  and  narrowed  towards  the  posterior 
end  of  the  pygidium,  where  they  connect.      The  marginal  furrow 


Genus  Agnostus. —  Vogdes.  .  389 

increases  in  width  going  backwards  as  far  as  the  posterior  lateral 
angles,  where  it  is  as  wide  as  the  lateral  lobe  of  the  p3'gidium, 
but  harrows  again  towards  the  extremity  of  the  pygidiuni.  The 
limb  increases  in  width  from  the  front  as  far  as  the  lateral  spines, 
behind  which  it  is  constricted;  at  the  anterior  end  it  is  angulated 
towards  the  axis,  in  the  rear  third  broadlj^  rounded. 

Locality.  8t.  John  group,  Portland  and  at  Hanford  brook,  St.  Mar- 
tin's. 

The  species  differs  but  slightly  from  Agnostus  fallax  YSiT.ferox  Tullb. 
from  the  Scandinavian  formation  at  Andrarum  with  Paradoxides  tessini. 

Agnostus  vir  var.  concmnus  Matthew,  1885.       Plate  ix,  fig.  13. 
This  variety  varies  but  slightly  from  Agnostus  vir. 

DIKELOCEPHALUS  ZONE. 
Section  LONGIFRONTES. 

Agnostus  americanus  Billings,  1860. 
Syn.  Agnostus  richmondensis  Walcott.  Plate  ix,  figs.  5  and  11. 
Diagnosis. — Head  oblong,  semi-oval,  rather  strongl}"  convex, 
most  elevated  at  the  posterior  quarter  of  the  length,  thence  de- 
scending with  a  depressed  convex  slope  in  all  directions  to  the 
sides  and  front.  Limb  verj^  narrow.  The  glabella  is  elongate 
oval,  width  ^  that  of  the  tvhole  head,  length  rather-  more  than  f 
the  length  of  the  head.  It  has  two  transverse  furrows  which 
completely  or  partially  divide  it  into  three  lobes.  The  anterior  fur- 
row extends  all  across  at  ^  or  a  little  more  of  the  length  from  the 
front.  The  posterior  furrow  is  interrupted  in  the  middle,  and  is 
only  distinctly  seen  on  each  side,  penetrating  ^  the  width,  while 
its  position  is  a  little  in  advance  of  the  posterior  third  of  the 
length  of  the  glabella.  The  space  between  the  two  inner  extrem- 
ities of  the  posterior  furrows  is  occupied  by  a  low  conical  tuber- 
cle, with  the  apex  directed  backwards.  Basal  lobes  small  and 
triangular.  Dorsal  groove  distinct.  Cheeks  divided  in  front  of 
the  glabella  by  a  furrow.  The  surface  is  ornamented  by  from  15 
to  20  irregular,  slightly  impressed  radiating  rugose  stride.  The 
pygidium  is  striated  like  the  head.  The  axis  has  three  lobes  with 
an  elongated  median  tubercle,  extending  across  the  anterior  and 
middle  lobes ;  the  posterior  lobe  is  equal  in  size  to  the  other  lobes. 

Locality.    Point  Levis,  Quebec. 

This  species  approaches  A.  trisectus  Salter,  which  occurs  at  Andrarum, 
Sweden  with  the  genus  Peltura. 


390  The  American  Geologist.  June,  1892 

Agnostus  canadensis  Billings,  1860.     Plate  ix,  fig.  9. 

Dlag)iosis. — Head  obtusely  oblong,  semi-oval,  width  a  little 
greater  than  the  length,  a  concave  border  nearly  as  wide  as  the 
glabella  all  around.  Glabella  in  width  less  than  |  the  width  of 
the  head,  and  in  length  a  little  more  than  |  the  length  of  the  head. 
Basal  lobes  small.  The  transverse  furrow  marking  the  frontal 
lobe  of  the  glabella  is  located  a  little  in  advance  of  the  mid- 
length  ;  the  tubercle  is  obscure  and  appears  to  be  indicated  by  the 
small  indentation  in  the  middle  of  the  transverse  furrow.  The 
cheeks  are  separated  in  front  of  the  glabella  by  a  furrow. 

The  author  doubtfully  figures  a  pygidium  of  this  species.  It 
has  a  similar  form  to  that  of  the  head  of  A.  canadensis  with  the 
concave  border  all  around  the  margin.  The  axis  is  obtusel}^  cla- 
vate,  and  marked  with  two  joints.  The  posterior  joint  is  large 
and  convex,  extending  quite  to  the  concave  border,  where  it  is 
full  half  as  wide  as  at  the  furrow  which  divides  the  two  joints. 
The  tubercle  is  situated  in  the  transverse  furrow  and  makes  a 
small  indentation  in   the  edge  of  the   posterior    joint. 

Tjocality.     Point  Levis,  Quebec. 

Agnostus  communis  Hall  and  Whitfield,  1877.   Plate  ix,  fig.  15. 

Diagnosis. — Head  subparaboloid,  wider  than  long.  Surface 
strongly  convex.  Glabella  nearly  equaling  ^  of  the  width  of  the 
head ;  anterior  third  separated  from  the  posterior  lobe  by  a  faint, 
transverse  furrow.  Central  part  of  the  glabella  ornamented  bj^ 
an  elongated  and  angular  tubercle.  Dorsal  furrow  distinct. 
Cheeks  separated  in  front  of  the  glabella  by  a  groove.  Basal 
lobes  triangular.      Limb  flattened.     Thorax  unknown. 

The  pygidium  with  a  flattened  limb,  which  is  ornamented  with 
lateral  spines.  Surface  strongly  convex ;  in  the  anterior  half ,  the 
dorsal  furrow  being  directed  gently  inward  for  half  their  length, 
and  then  suddenly  deflected  outward,  with  a  slight  curvature,  be- 
coming obsolete  a  little  behind  the  middle  of  the  length.  A.n 
elongated  angular  node  marks  the  axis  near  its  anterior  margin. 
Surface  of  the   head  and  pygidium   smooth. 

Locality.     White  Pine,  Nevada. 

This  species  is  of  the  type  Agnostus  cyclo'pyge  Tullberg. 

Agnostus    coloradensis  Shumard,  1861.  Plate  ix,  fig.  16. 
•  The  description  was   drawn   from   a  single  example  found   in 
Burnet  county,    Texas,    near  the  mouth  of  Morgan's  creek;  the 


Genus  Agtiostus. —  Vogdes.  391 

author  states  that  there  is  no  fissure  extending  from  the  glabella 
to  the  anterior  margin.  The  absence  of  this  groove  ma}-  be  due  to 
the  state  of  preservation.  This  species  agrees  in  every  other  re- 
spect with  A.  neon.  Agnostus  neon  differs  from  A.  commuma  in 
minute  points,  especially  in  the  absence  of  the  tubercle  on  the 
glabella. 

Agnostus  orion  Billings,  1860  (cf.  A.    jnsiformis  Linne). 
Plate  IX,  fig.  12. 

Diiignosia. — Length  and  breadth  about  equal,  sub-circular,  con- 
vex, a  very  narrow  margin  all  around.  Glabella  not  quite  f  the 
whole  length,  very  convex;  a  transverse  furrow  at  one-third  the 
length  from  the  apex ;  small  triangular  basal  lobes  without  a  median 
tubercle.     Cheeks  divided  in  front  of  the  glabella  by  a  furrow. 

Locality.     Point  Levis,  Quebec. 

The  same  term  was  used  by  Barrande  in  1846  for  a  species  of  this 
genus.  If  this  species  differs  from  A.  pisiformisii  is  only  in  the  absence 
of  the  median  tubercle,  which  may  be  due  to  its  state  of  preservation. 
There  is  a  slight  indication  of  the  tubercle  on  one  of  my  cabinet  speci- 
mens from  Point  Levis.  A  pygidium  from  the  same  locality  is  similar 
to  that  of  Agnostus  insiformis. 

Agnostus  josepha  Hall,  1863.  Plate  ix,  fig.  17. 

Diagnosis. — Head  semi-elliptical,  margined  by  a  flattened  or 
concave  narrow  limb;  genal  angles  produced  into  short  spines. 
Glabella  prominent,  narrow,  extending  about  f  the  length  of  the 
head,  and  crossed  by  a  shallow  furrow  near  the  anterior  end.  The 
posterior  lobe  is  marked  by  an  oblique  furrow  on  each  side;  a 
small  node  on  the  summit  at  the  anterior  termination.  The  trian- 
gular space  on  each  side  between  the  transverse  and  oblique  fur- 
rows is  like- wise  elevated  into  a  low  node.  The  posterior  central 
portion  is  gibbous.  The  ba?al  lobes  small  and  triangular  in  form. 
Cheeks  divided  in  front  of  the  glabella  b)^  a  furrow.  Pygidium 
of  the  same  form  as  the  head.  Axis  prominent,  subquadrate, 
wider  than  long,  nearly  ^  the  length  of  the  pygidium,  bearing  a 
node  or  short  spine  on  its  posterior  extremity ;  sides  and  body  of 
the  pygidium,  outside  of  the  axis,  highly  convex. 

Locality.  Trempealeau  and  elsewhere  on  the  Mississippi  about  lake 
Pepin,  Wisconsin.  The  species  occurs  with  Anomocare  wisconsensis  and 
Ptychaspis  granulosa. 


392  The  American  Geologist.  jmie,  189^ 

Agnostus  richmondensis  Walcott,  1884.  Plate  ix,  fig.  11. 
Diagnosis. — Head  moderately  convex,  length  and  breadth  equal. 
Glabella  f  the  length  and  a  little  more  than  ^  as  wide  at  the  base 
than  the  width  of  the  head;  elongate,  conical  in  outline, 
strongly  defined  by  the  dorsal  furrows,  with  the  anterior  third 
separated  by  a  distinct  transverse  furrow ;  a  little  less  than  mid- 
way between  this  furrow  and  the  posterior  margin,  a  short  furrow 
penetrates  from  each  side  towards  the  base  of  a  minute  tubercle 
situated  on  the  median  line.  Basal  lobes  small,  triangular. 
Cheeks  more  convex  than  the  glabella,  separated  in  front  of  the 
glabella  by  a  furrow.  Limb  narrow.  Surface  ornamented  by 
slightly  irregular  depressed  lines  that  indent  the  surface  from  the 
margin  nearly  to  the  edge  of  the  strong  dorsal  furrows.  Surface 
smooth  under  an  ordinary  magnifying  power. 

Locality.    Prospect  mountain,  Nevada. 

This  species  is  identical  with  Agnostus  americanus  Billirgs. 

Agnostus  maladensis  Meek,  1873,  aff.  Agnosfas  joseplia. 
The  author  proposes  this  name  for  a  species  from  Malade  City, 
Utah,  which  is  closely  allied  to  Agnostus  joscplxi  Hall,  except  that 
the  specimens  do  not  exhibit  the  spines  on  the  genal  angles  of  the 
head;  the  author  remarks  "none  of  which  are  in  a  condition 
to  remove  all  doubt  on  this  point." 

Section  LIMBATI. 
Agnostus  bidens  Meek.  Plate  x,  fig.  5. 
Diagnosis. — Head  moderately  convex,  slightly  wider  than  long, 
bordered  by  a  rounded  margin  with  a  strongly  defined  marginal 
groove.  Glabella  convex,  narrow,  more  than  |  the  length  of  the 
head,  converging  anteriorly,  sub-angular  in  front;  two  oblique 
furrows  posterior  to  the  center  enter  from  each  side,  and  unite 
just  in  advance  of  a  small  node,  on  the  center  of  an  elevation,  de- 
fined behind  by  a  transverse  furrow  that  bends  backwards;  be- 
tween this  furrow  and  the  occipital  furrow  a  narrow  band  extends, 
widening  out  laterally,  forming  the  basal  lobes.  Dorsal  furrow 
distinct.  Cheeks  convex  and  sloping  rapidly  to  the  marginal 
groove  from  the  somewhat  elevated  central  portion.  Thorax  un- 
known. The  pygidium  is  armed  with  lateral  spines,  and  is 
strongly  convex.  Axis  conical,  extending  more  than  f  of  the  en- 
tire length,  ornamented  with  an  elongated,  angular  tubercle  on  the 


Ge7ius  Aff7iostns. —  Vogdex.  393 

anterior  portion,  with  a  transverse  furrow  just  before  it,  separating 
a  narrow  anterior  portion;  in  some  examples  a  faint  transverse 
furrow  crosses  back  of  the  tubercle.  Surface  of  the  head  and 
pygidium  finely  granulose. 

Locality.  Gallatin  City,  Montaaa,  also  in  the  Eureka  District  of  Ne- 
vada and  elsewhere. 

Agnostus  tumidosus  Hall  and  Whitfield,  1877.     Plate  x,  fig  8. 

Diagnosis. — Head  highly  dome-shaped  in  outline,  slightly  con- 
tracted near  the  occipital  border,  very  convex.  Limb  narrow, 
flattened.  Dorsal  furrow  distinct.  Glabella  small,  less  than  f 
as  long  as  the  head,  conical  and  very  convex,  especiall}'  tumid  in 
the  lower  part ;  the  central  tubercle  marked  near  its  edge  by  a  very 
slight  line  which  presents  the  appearance  of  a  border  surrounding 
it.  Frontal  lobe  about  \  of  the  length  of  the  glabella.  Basal 
lobes  triangular  and  minute.  Thorax  unknown.  The  highl}^ 
dome-shaped  outline  with  the  form  and  markings  of  the  glabella 
distinctly  mark  this  species. 

Locality.  Eureka,  Nevada.  The  species  is  of  the  type  A.  quadratus 
Tullberg. 

Agnostus  interstrictus  White,  1874.     Plate  x,  fig.  6. 

Diagnosis. — This  species  of  the  type  A.  fallax  Linrs.  is  ellip- 
tical in  form  with  a  smooth  surface.  The  head  is  broader  than 
long.  Limb  narrow,  forming  a  narrow  linear  depression  between 
it  and  that  portion  of  the  head  which  it  incloses.  Glabella  bilobed, 
conical,  well  defined  by  the  dorsal  furrows,  and  sharply  rounded 
in  front.  A  minute  tubercle  on  the  median  line;  near  the  poster- 
ior end;  the  frontal  lobe  is  marked  off  by  a  shallow  transverse 
furrow.  Thorax  of  two  joints,  narrower  than  the  head  and 
P3'gidium,  giving  the  body  the  appearance  of  being  constricted  at 
the  middle.  Axis  broad,  both  its  joints  tumid  at  the  ends,  where 
they  reach  the  dorsal  furrows;  lateral  lobes  very  narrow,  pleurae 
about  as  wide  as  long,  each  pleurae  tumid  and  rounded  at  the  ex- 
tremities. Pygidium  in  form  like  the  head.  Axis  a  little  longer 
than  the  glabella,  moderately  convex,  with  a  minute  tubercle  on 
the  median  line  near  the  anterior  end.  Sides  between  the  mar- 
ginal furrow  and  axis  convex.  The  lateral  angles  of  the  pygid- 
ium are  produced  into  sharp  spines.  The  basal  lobes  of  the  gla- 
bella are  very  minute. 

Locality.  Antelope  Springs,  Utah. 


394  The  American  Geologist.  june,  1892 

Section  L^VIGATI.  The  dorsal  grooves  marking  the  glabella 
and  axis  of  the  thorax  and  pygidium,  are  wanting  or  faintly  indi- 
cated. Crust  smooth,  sometimes  with  slight  indications  of  striae. 
Limb  on  the  head  disappearing;  on  the  pygidium  it  becomes  broad. 
{Agnostus  Icvvigatufi.  Dalm.,  plate  X,  fig.  8). 

Agnostus  disparilis  Hall,  1863.  Plate  x,  fig.  15. 
Diagnosis. — Head  semi-elliptical,  convex  towards  the  posterior 
side,  and  abruptly  sloping  in  front;  length  and  breadth  nearly  as 
3  to  4,  a  little  concave  on  the  posterior  margin  and  marked  near 
the  edge  by  a  narrow  groove  on  each  side  of  the  middle;  the  centre 
slightly  elevated  close  to  the  margin.  The  limb  is  a  little  wider 
in  front  than  at  the  sides.  The  pygidium  (?)  is  a  little  wider  than 
long.  The  trilobation  extends  nearly  to  the  posterior  extremit}^, 
and  is  separated  from  it  only  by  a  narrow  border.  The  axis  is 
fully  once  and  a  half  as  wide  as  the  side  lobes,  somewhat  flattened 
on  the  summit,  and  very  distinctly  limited  by  the  dorsal  furrows. 
The  pygidium  figured  with  this  species  ma}'  be  that  of  the  genus 
Microdiscus. 
Locality.    Oseola  Mills,  on  tlie  St,  Croix  river,  Wisconsin. 

Agnostus  parilis  Hall,  1863.  Plate  x,  fig.  4. 
Diagnosis. — Head  semi-elliptical;  length  and  breadth  about 
equal,  very  convex  in  the  posterior  part,  and  curving  downwards 
to  the  anterior  margin.  The  central  portion  of  the  posterior  part 
is  limited  by  a  faint  curving  groove;  and  anterior  to  its  limits 
there  is  a  slight  elevation,  which  may  have  a  node  on  the  surface 
of  the  crust.  The  posterior  margin,  just  within  the  angles,  is  pro- 
duced in  a  minute  node.  The  limb  gradually  expands  from  the 
posterior  angles  to  the  front,  where  it  becomes  well  defined.  The 
pygidium  is  slightly  truncated  at  the  anterior  angles,  the  marginal 
rim  narrower  towards  the  articulating  border.  The  central  part 
is  slightly  more  elevated  and  limited  by  furrows  diverging  from 
the  anterior  margin.  On  the  median  line,  at  a  point  ^  the  length 
from  the  front  margin,  there  is  a  distinct  elongated  tubercle. 
Locality.    Shores  of  lake  Pepin. 

Agnostus  prolongus  Hall  and  Whitfield,  1877.     Plate  x,  fig.  10. 
Diagnosis. — Head  elongated,  or  very  high  dome-shaped  in  out- 
line.     Surface  depressed,  convex  in  front  and  gradually  rising  to 
near  the  occipital  border,  where  it  becomes  low,  tumid.      Glabella 


Genus  Ag7iost us. —  Vogdes.  395 

very  indistinct,  of  conical  form,  with  triangular  basal  lobes.  Limb 
narrow,  somewhat  rounded,  gradually  fading  out  along  the  postero- 
lateral angles.  Pygidium  (?)  much  like  the  head,  but  much  shorter 
in  proportion  to  its  width.  The  axis  occupies  more  than  ^  of  the 
width,  short  and  rounded,  obconical,  ornamented  by  a  node  in  its 
upper  end,  and  divided  across  by  a  doubly  curved  transverse  fur- 
row near  the  lower  end.  Dorsal  furrows  distinct.  Limb  flattened. 
Locality.  Eureka,  Nevada. 

Section  FALLACES. 
Agnostus  seclusus  Walcott,  1884.      Plate  x,  fig.  16. 

Diagnosis. — Head  strongly  convex,  a  little  longer  than  wide^ 
with  a  slight  contraction  posteriorly.  Limb  narrow  with  a  distinct 
groove  between  it  and  the  cheeks.  Dorsal  furrows  well  defined. 
Basal  lobes  distinct.  Glabella  about  half  the  length  of  the  head, 
strongly  convex  and  squarely  truncated  in  front;  at  about  the  an- 
terior third  a  broad,  short  furrow  penetrates  on  each  side  a  Short 
distance,  and  posteriorly  a  rounded  node  is  separated  from  each 
lateral  angle  by  slight  furrows,  forming  the  basal  lobes.  The 
cheeks  slope  rapidly  towards  the  marginal  groove,  on  the  sides 
and  more  gradually  to  the  front.      Surface  finely  granulose. 

Locality.      Secret  Canon  shales,  Eun^ka  District,  Nevada. 

ASAPHUS  ZONE. 

Section  IV,  ARTHRORHACHIS,  type  Agnostus  tardus   Barr. 
Agnostus  galea  Billings,  1865.     Plate  ix,  fig.  6. 

The  author  describes  in  The  Palaeozoic  Fossils  of  Canada,  Vol. 
1,  1865,  p.  291,  Agnostus  gajlm  and  A.  fahius  from  Table  Head 
and  Pistolet  bay,  Newfoundland.  Both  these  species  are  of 
Lower  Siluric  types,  the  first  of  Agnostus  tardus  Barr,  and  the 
second  of  A.  lentifonnis  Ang.  The  species  appear  with  the  gen- 
era Asajihus,  lUeenus  and  Triarthrus  Jischeri.,  etc. 

Diagnosis. — Head  strongly  convex.  Limb  narrow.  Glabella 
convex,  strongly  elevated  above  the  general  surface,  occupying  . 
about  f  of  the  whole  length  of  the  head.  Smooth,  no  tubercle, 
but  with  slight  indentations  on  each  side,  at  about  the  mid-length. 
Dorsal  furrows  distinct.  Basal  lobes  triangular.  Pygidium  in 
contour  and  convexity,  like  the  head.  Axis  strongly  convex,  well 
defined  all  round  by  the  dorsal  furrows;  a  furrow  runs  all  across 
at  ^  the  length  from  the  apex ;  a  short  one  on  each  side  at  f  the 


396  The  Arnerican  Geologist.  June,  i892 

length  from  the  apex.  The  tubercle  forms  a  longitudinal  medium 
lobe  in  the  anterior  |  of  the  axis.  The  tubercle  is  at  the  anterior 
margin,  slightly  elevated  above  the  general  convexit}"  of  the  axis,  it 
is  less  elevated  just  over  the  anterior  pair  of  furrows,  but  behind 
this  point  it  rises  to  twice  the  hight  and  terminates  abruptly 
at  the  posterior  furrow.  The  anterior  lobes  of  the  axis  are  dis- 
tinctly separated  from  the  tubercle  b}^  a  narrow  groove;  the 
second  two  are  not.  Surface  apparently  smooth,  but  with  indi- 
<3ations  of  small  wrinkles  which  unite  with  each  other,  so  as  to 
give  a  reticulated  aspect,  similar  to  that  of  A.  reticulatus  Ang. 
The  species  differs  from  A.  tardus  Barr,  in  having  a  shorter  axis 
in  the  pygidium,  and  in  having  the  node  of  uniform  hight  its 
whole  length. 

Agnostus  fabius  Billings,  1865.  Plate  ix,  fig.  10. 
Diagnosis. — Head  semi-elliptical,  uniformly  and  moderately 
convex.  Liml)  very  narrow.  Grlabella  scarcely  elevated  above  the 
general  surface,  not  defined  in  front;  obscurely  so  in  the  posterior 
half  by  the  dorsal  furrows,  which  are  parallel,  and  disappear 
about  the  middle  of  the  head.  Basal  lobes  small,  triangular. 
Pygidium  slightly  more  elongated  than  the  head.  Limb  narrow, 
flat.  Axis  about  ^  the  whole  width;  it  has  two  pairs  of  transverse 
furrows,  the  posterior  reaching  the  median  line,  where  there  is  a 
small  rounded  tu})ercle,  located  slightly  behind  the  mid-length  of 
the  axis.  The  anterior  furrows  are  half  way  between  the  tuber- 
cle and  the  front  margin,  their  inner  extremities  separated  by 
about  one-third  the  width  of  the  axis. 


